Question

The read function has it’s first argument as pointer to an array to store the n bytes(mentioned by the second argument) in the file…

The query is,

if i have created 2 objects of class x..

then,

x stack[2]; 

Assume i’ve filled the 2 object contents, opened a file ‘xyz'(using fstream i’ve created object file & used the command file.open("xyz",ios::in|ios::out) and filled the file with contents of 2 objects using write..

now if i use this command

file.read((char*) &stack[1],sizeof(stack[0]))

will the stack[1] have the contents of stack[0],

i.e. will the read function take it’s first argument address as &stack[1] or will it consider &stack[0] ??

Update:The code which is used to reverse the contents of the stack

//
//To reverse the contents of the objects

    #include "stdafx.h"
    #include<iostream>
    #include<fstream>
    #include<iomanip>

    using namespace std;

    class Inventory
    {
     char name[10];
     int code;
     int cost;

     public:

     void readdata();
     void writedata();
    };

    void Inventory::readdata(void)
    {
     cin>>name;
     cin>>code;
     cin>>cost;
    }

    void Inventory::writedata(void)
    {
     cout<<setiosflags(ios::left)
     <<setw(10)<<name
     <<resetiosflags(ios::right)
     <<setw(10)<<code
     <<setprecision(2)
     <<setw(10)<<cost
     <<endl;
    }

    int main()
    {
     Inventory item[3];

     fstream file;

     file.open("Stock",ios::in|ios::out);

     cout<<"Enter details for three items\n";

     for(int i=0;i<3;i++)
     {
       item[i].readdata();
       file.write((char*) &item[i],sizeof(item[i]));
     }
     file.seekg(0);

     cout<<"\nOutput\n\n";

     for(int i=0;i<3;i++)
     {
         file.read((char*) &item[2-i],sizeof(item[i]));
     }

     for(int i=0;i<3;i++)item[i].writedata();
     file.close();
     return 0;

    }

Answer 1

Try this:

file.open("Stock",ios::in|ios::trunc|ios::out);